Method and devices for controlling operations of a central processing unit

ABSTRACT

Provided is a method in a control circuitry controlling the operations of a central processing unit, CPU. The CPU is associated with a nominal clock frequency. The CPU is further coupled to an I/O range and configured to deliver input to an application. According to the method, the control circuitry controls ( 110, 150 ) the CPU to poll the I/O range for input to the application. The control circuitry also monitors ( 120, 160 ) whether or not each poll results in input to the application and adjusts ( 140 ) a clock frequency at which the CPU operates to a clock frequency lower than the nominal clock frequency if a pre-defined number of polls resulting in no input is detected ( 130 ). A control circuitry and a central computer server of an automated exchange system are also provided.

TECHNICAL FIELD

The present invention relates to a method and devices for controllingoperations of a Central Processing Unit (CPU), and more particularly itrelates to a control circuitry configured to interact with the CentralProcessing Unit.

BACKGROUND

The roll out of Internet and the following continuous investment ininfrastructure providing network access to the Internet have madeinformation exchange easy throughout the globe. With the global accessto all sorts of different computer systems the Internet provides for andthe increasing use of the Internet, the numbers of data messagesdirected to central computer servers of the computer systems areincreasing. Many computer systems are connected to the Internet toprovide access to functionalities for a select group of people or forthe public. Depending on the functionalities and the interest peoplehave in accessing the functionalities, different computer systemsreceive different amounts of data messages.

An automated electronic exchange is one such type of computer systemwherein users of the automated electronic exchange in one way or anotherconnect to a central computer server which is part of the automatedelectronic exchange, usually through the Internet, and submit datamessages to the central computer server.

Due to technological advances in computing technology, transactiontechnology and information technology in the past ten to twenty years,financial technology has had a very rapid development rate. This rapiddevelopment has resulted in computer systems trying to cope withincreasing numbers of companies and people trying to connect to thesesystems. The increasing numbers of users being connected to electronicexchange systems have increased the amount of data messages sent intothe system.

A conventional electronic exchange typically receives input data in theform of data messages from external devices, trader terminals, used bytraders to send orders and/or quotes to the electronic exchange. Theorders/quotes may relate to buying and/or selling of any type oftradable asset. In particular the input data can relate an order messagethat represents the placing of a new buy or sell order or a new quote.Furthermore, the development of algorithmic trading, i.e. computersprogrammed to analyze data and autonomously act on the data bysubmitting orders to an electronic exchange, has exponentially increasedthe amount of data messages being sent to the electronic exchangesystems.

In order for computer systems to perform some kind of action in responseto the data messages sent by users of the computer system the datamessages have to be received in some kind of input/output device anddetected as input.

Traditionally one way of detecting a data message input in a computersystem has been to do it in an interrupt driven process. Input receivedby an input/output (I/O) device of the computer server of the computersystem has triggered an interrupt request to be issued. A centralprocessing unit (CPU) of the computer system typically breaks(interrupts) its current computations and stores the current state whenreceiving the interrupt request. The CPU then processes a set of storedinstructions related to the specific interrupt request. When allinstructions related to the interrupt request have been completed, theCPU reverts back to the stored state and continues processing the set ofinstructions it was processing prior to the interrupt request. Thetransition between states of processing in the CPU is typically called acontext switch. When no interrupt request is received by the CPU, orwhen the CPU is finished with the current processing, the CPU can revertto an idle mode.

Another technique to detect input to a computer system is to have theCPU poll an I/O device for input, i.e. continuously check the I/O deviceuntil input is found, and then process the input when a poll rendersinput.

The interrupt driven detection and handling of input has the advantagethat the CPU when not processing input can process other instructions.The polling technique has the advantage that input generally is detectedand processed earlier as the CPU expects to find and is ready to processany input each poll (check) of the I/O device might render.

A disadvantage with the interrupt driven technique is that, whenreceiving huge amounts of data messages for computer systems requiring ahigh throughput, the interrupt driven process may be experienced asgiving rise to a too high latency. Latency is defined as the time froman input data message is received by the computer system until thecomputer system has completed processing the data message and is readyreceive a new data message. The interrupt driven techniques is thereforeless suitable for systems with low latency requirements.

A disadvantage with the polling technique is that, while it allows for alow latency system, there is a risk that the CPU is constantly workingat full load just polling the I/O device even at times when there is noinput to retrieve. For most computer systems, the data messages do notarrive in a steady stream but the amount of data messages directedtowards the computer system varies quite a lot over time with peaks andtroughs. Thus while, the polling techniques are suitable for periodswith peak load, polling for input is not particularly suitable forperiods of trough load as large numbers of polls resulting in no inputhave to be performed, so-called negative polls. The negative polls ofthe polling techniques cause unnecessarily high processing load as wellas energy consumption of the CPU.

For many computer systems a swift change in load is a problem, forautomated electronic exchanges it is a particular problem. Sinceinformation is easily spread globally, many users of an automatedelectronic exchange tend to act on the same information at almost thesame time. Therefore peaks often are concentrated around occasions wheninformation, that in one way or another might change the appreciationmade by users connected to the automated electronic exchange, isreleased somewhere in the world. The number of data messages directedtoward the automated electronic exchanges, hence shifts very drasticallybetween peaks and troughs throughout a trading day.

It would thus be advantageous to provide a more flexible and efficientway of processing input received in a computer system.

SUMMARY

An object of the embodiments of the present invention is to provide amethod and apparatus that allow a CPU to process input in a flexible andefficient way.

The above stated object is achieved by a method, a control circuitry anda computer server according to the independent claims.

A first embodiment provides, a method for controlling the operations ofa Central Processing Unit (CPU) associated with a nominal clockfrequency. The CPU is coupled to an input/output (I/O) range andconfigured to deliver input to an application. The method comprisescontrolling the CPU to poll the I/O range for input to the application.The polling is repeated until a poll results in input to theapplication. The method further comprises monitoring whether or not eachpoll results in input to the application and adjusting a clock frequencyat which the CPU operates, to a predetermined first clock frequencylower than the nominal clock frequency, if a pre-defined number of pollsresulting in no input is detected.

A second embodiment provides a control circuitry for controlling a CPUassociated with a nominal clock frequency. The CPU is coupled to an I/Orange and configured to deliver input received at the I/O range to anapplication. The control circuitry is arranged to instruct the CPU topoll the I/O range for input to the application and to monitor whetheror not a poll results in input to the application. The control circuitryis further arranged to adjust a clock frequency at which the CPUoperates, to a predetermined first clock frequency lower than thenominal clock frequency, if a pre-defined number of polls of the I/Orange resulting in no input is detected.

A third embodiment provides a central computer server of an automatedexchange system for matching orders received from clients. The centralcomputer server comprises an I/O range for receiving orders from clientsin the automated exchange system and a CPU associated with a matchingprocess for matching received orders. The CPU is coupled to the I/Orange. The central computer server further comprises a control circuitryin accordance with the second embodiment described above for controllingthe CPU to poll the I/O range for received orders for input to thematching process.

An advantage of some of the embodiments disclosed herein is thatprocessing by a CPU can be performed with lower energy consumption whileproviding for rapid response to input. These and other aspects andadvantages of different embodiments will become apparent from thefollowing detailed description and from the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description of embodiments of the invention, referencewill be made to the accompanying drawings of which:

FIG. 1 is a flow diagram illustrating an embodiment of a method forcontrolling operations of a CPU.

FIG. 2 is a flow diagram illustrating an alternative embodiment of amethod for controlling operations of a CPU.

FIG. 3 is a flow diagram illustrating another alternative embodiment ofa method for controlling operations of a CPU.

FIG. 4 is a schematic block diagram illustrating a computer servercomprising a CPU and a control circuitry according to an exampleembodiment.

FIG. 5 is a schematic illustration of an automated exchange systemincluding an embodiment of an automated exchange.

FIG. 6 is a schematic block diagram illustrating a layered topology ofdata processing in accordance with some embodiments.

DETAILED DESCRIPTION

Some example embodiments will now be described in more detail with useof the figures.

Depending on the use and configuration of a computer system differentcapabilities are provided and also required of it. For computer systemsprocessing input data in a Central Processing Unit (CPU) it is typicallyadvantageous to detect and process data as quickly as feasible in orderto potentially be able to service as many inputs as possible. Asdescribed above it is of interest that the CPU processes input in aflexible and efficient way. Embodiments to be described in furtherdetail below achieve this by controlling the operations of the CPU byuse of a frequency adjusting control circuitry. By controlling theoperations of the CPU as well as the frequency at which the CPU operatesadvantageous effects in regards to thermal energy, processing power,latency and throughput can be achieved.

FIG. 1 is a flowchart illustrating an example embodiment of a method forcontrolling operations of a CPU. The example method is adapted for usein a control circuitry for controlling the operations of the CPU. TheCPU is associated with a nominal clock frequency. The CPU is furthercoupled to an input/output, I/O, range and configured to deliver inputto an application. The application may be practically any type ofapplication program processing input, such as an order matching processof an automated exchange system.

For illustrative purposes below, it is envisaged that the operatingfrequency of the CPU when the method is initialized, is the nominalclock frequency. However, the actual configuration and architecture of aparticular system will of course determine an actual operating frequencyfor the particular system.

The method outlined in FIG. 1 in step 110, comprises controlling the CPUto poll the I/O range for input to the application. The method furthercomprises a step 120 of monitoring whether or not each poll results ininput to the application. If it is detected in the step 120 that a pollresults in input to the application, the CPU is controlled to return theinput to the application in a step 190. If a poll is a negative poll,i.e. results in no input to the application, it is determined in a step130, if a pre-defined number (X) of negative polls have been detected.

The number of consecutive negative polls may for example be counted byincrementing an accumulator register of the CPU for each negative poll.The accumulator register may also, when a poll is positive i.e. rendersinput to the application, be reset. The accumulated number ofconsecutive negative polls may then be compared to the pre-definednumber. When it is detected that the pre-defined number of consecutivenegative polls has been performed, the frequency at which the CPUoperates is adjusted to a pre-determined first clock frequency lowerthan the nominal clock frequency in a step 140. Assuming that the CPUoperated at the nominal clock frequency when the method was initiated,performing the step 140 will thus lead to a reduction of the clockfrequency at which the CPU operates. In a step 150 the CPU is controlledto again poll for input to the application, which thus is carried out atthe reduced frequency following the step 140. As a consequence the CPUwill continue to poll the I/O range for input to the application lessfrequently, which reduces the processing load as well as energyconsumption of the CPU. When a poll at the reduced frequency results ininput to the application, the CPU is controlled to return the input tothe application in the step 190. Thus, according to the example methodillustrated in FIG. 1, the CPU is controlled to repeat the polling untila poll results in input to the application. But the frequency at whichthis polling is carried out may be changed depending on the amount ofdetected negative polls.

The pre-defined number of negative polls to be detected before anadjustment of the operating frequency of the CPU can be set to anynumber which is considered appropriate in the particular applicationscenario as a trigger for adjusting down the operating frequency. Thenumber which is considered appropriate may depend on the type of systememploying the method and also on a tradeoff between thermal efficiencyand input detection speed. By allowing a higher number of negative pollsbefore adjusting down the operating frequency, a high detection speedcan be achieved at the risk of worse long term thermal efficiency.However, if thermal efficiency is more important a smaller number ofnegative polls should be allowed before adjusting the operatingfrequency. The pre-defined number may be optimized based on the expectedload of the system and the requirements put on the system.

In an example embodiment, the operating frequency is reduced directlyafter detecting a single negative poll. The configuration of thepre-defined number to one has the advantage that it results in a highthermal efficiency. Hence in some embodiments, the pre-defined numberequals one. In these embodiments the number of negative polls may bekept low by continuing polling at a reduced speed as soon as a negativepoll is detected. The total amount of energy the CPU wastes on negativepolls may thus also be kept low. At the same time the system stillallows for a high throughput as latency is not increased when a positivepoll is followed by another positive poll

By reducing the clock frequency at which the CPU operates the amount ofnegative polls can be kept down to assure that the CPU is not wastingenergy by just polling for input when no input is available. However,the processing by the CPU of any received input at the reduced frequencywill lead to increased latency in comparison to the CPU operating at thenominal frequency. The latency is increased as each clock cycle used toprocess the input is longer. Therefore it is advantageous to increasethe operating frequency of the processor for every input detected whenthe processor is operating at the reduced clock frequency. Hence,according to some example embodiments, the method illustrated in FIG. 1further comprises an optional step 180 in which the clock frequency atwhich the CPU operates is adjusted to a predetermined second clockfrequency higher than the reduced clock frequency set in the step 140.The step 180 is performed if it is detected in the step 160 that a pollresults in input to the application.

In some embodiments, the predetermined second clock frequency equals thenominal clock frequency in other embodiments the predetermined secondclock frequency is higher than the nominal clock frequency. Byincreasing the operating frequency of the CPU, to the nominal clockfrequency associated with the CPU, the processing of a received inputcan be performed using less time. The increase of the operatingfrequency thus leads to reduced latency than if processed while theprocessor operates at the reduced frequency. As increased operatingfrequency leads to reduced latency it is further advantageous toincrease the operating frequency of the CPU to a frequency higher thanthe nominal clock frequency associated with the CPU. This may bepossible for a limited period if the CPU e.g. has been cooling down byoperating at the reduced frequency for some time as will be furtherexplained below in connection with another example embodiment.

In some embodiments the polling is performed in response to reception ofan instruction from the application, step 100. The instruction may alsospecify to poll the I/O range for input to the application until a pollresults in input to the application.

In some embodiments the control circuitry is also configured to detectpolling of an I/O range. The control circuitry is configured to monitorread operations on the I/O range and a poll resulting in no input isdetected by detecting a return to the same instruction to read the I/Orange within a pre-determined number of instructions.

FIG. 2 is a flowchart illustrating some procedural steps of a so-calledimplicit method according to an example embodiment. The method isreferred to as an implicit method since there is no reception of anexplicit instruction to poll the I/O range as in the method illustratedin FIG. 1. While an application in the embodiment described in FIG. 1typically issues an explicit poll instruction, this may not always bethe case. Some applications may, instead of an explicit poll instructionto the CPU, be configured to perform polling and control the pollingwithin the application program code. For example, an application may beconfigured to repeatedly read a certain I/O port or an I/O range untilinput is found, thus implicitly performing polling. Hence in someembodiments including the method in the example embodiment of FIG. 2,polling is instead detected.

In the example embodiment, a control circuitry controls the operationsof a Central Processing Unit (CPU) associated with a nominal clockfrequency. The CPU is coupled to an input/output (I/O) range andconfigured to deliver input to an application. The method comprises astep 200 of detecting polling of an I/O range for input to theapplication.

In the step 210, a predetermined number of polls not resulting in input,i.e. negative polls are detected. This is achieved by the controlcircuitry monitoring whether or not each poll results in input to theapplication. In some embodiments, the polling of an I/O range isdetected by the control circuitry monitoring read operations on the I/Orange, and a poll resulting in no input is detected by detecting areturn to the same instruction to read the I/O range within apredetermined number of instructions.

On detecting the predefined number of negative polls the clock frequencyat which the CPU operates, is in the step 220 adjusted down to apredetermined first clock frequency lower than the nominal clockfrequency, i.e. to a reduced clock frequency.

Some embodiments of the method illustrated in FIG. 2 also comprises astep 230 of detecting a positive poll, i.e. a poll rendering input tothe application, by monitoring the outcome of each poll while the CPU isoperating at the reduced frequency. On detecting a positive poll, theoperating frequency of the CPU is, in a step 240, adjusted up to asecond predetermined clock frequency.

By detecting the polling of an I/O range the implicit method allowsapplications programmed to, for example, poll an I/O range by issuingread operations to also benefit from the method. Thus, even olderapplications not configured for requesting polling from a CPU maybenefit from the claimed invention. In some embodiments, the monitoringof read operations on the I/O range may be limited to a particular I/Oport, I/O address or an I/O sub range, typically assigned to thereception of input in order to speed up the monitoring and detectionprocess.

Some CPUs allow “overclocking” (n.b. operating a CPU at a frequencyhigher than the associated nominal clock frequency) or some other methodof boosting the operations of the CPU. The method of the exampleembodiment illustrated in FIG. 3 is particularly suited for use withCPUs suitable for “overclocking”.

FIG. 3 is a flow diagram illustrating a further example embodiment of amethod for controlling operations of a CPU. The method of FIG. 3 bearssimilarities with some of the method steps disclosed in FIG. 1, inparticular steps 100-160 are similar and will not be described in detailagain.

In a step 370 the method determines, when a poll results in input ineither of the steps 120 or 160, a temperature of the CPU.

In another step 375 of the method, the temperature of the CPU iscompared against a predefined temperature threshold. By the comparison,it is possible to detect if the CPU thermally is able to cope with atemporary boost in operating frequency without it leading to overheatingof the CPU. In a step 380 the clock frequency at which the CPU operatesis adjusted to a predetermined third clock frequency higher than thenominal frequency, if the temperature of the CPU is below thetemperature threshold. Typically, operating a CPU above the nominalclock frequency is not sustainable over time, due to overheating of theCPU. However, as the disclosed method reduces the operating frequency ofthe processor below the nominal clock frequency on detecting apredetermined number of negative polls, the temperature of the CPU mightallow the CPU for a short time to operate at a frequency higher than thenominal clock frequency associated with the processor without causingproblems related to overheating.

In a further step 390 the CPU is controlled to return the detected inputin either of step 120 or step 150 to the application.

When polling for input instead of using an interrupt driven process, theCPU continuously tries to check the I/O range for input as often aspossible. The CPU thus works at full capacity polling for input.Typically the nominal clock frequency associated with the CPU is afrequency at which the manufacturer guarantees that the CPU sustainablycan operate at full load. By, in step 370, measuring a temperature ofthe processor on receiving and detecting input to be processed, it ispossible to determine if the CPU recently have been operating at orclose to a maximum sustainable operating frequency. If it is determined,in step 375, that the CPU have been operating below the maximumsustainable clock frequency of the CPU, a short period of increasedoperation and the following increased heat generation might beallowable. If on the other hand, in step 375, it is determined that theCPU have been operating above the maximum sustainable operatingfrequency of the CPU, an increase of the operating frequency to a thirdoperating frequency higher than the nominal clock frequency might leadto instability. Hence, by comparing the measured CPU temperature againsta predetermined threshold value suitable for the CPU in step 375 it ispossible to determine if it is wise to increase the operating frequencyof the CPU to a predetermined third frequency higher than the nominalclock frequency. If the measured temperature is determined to be belowthe threshold value it is possible to increase the operating frequencyand reduce the latency, to allow the input to be processed faster.

If it is detected in step 375 that the temperature of the CPU is abovethe threshold value, it might not be wise to adjust the operatingfrequency of the CPU to a frequency higher than the nominal clockfrequency. The nominal clock frequency is typically associated with asustainable operating frequency and in some embodiments the clockfrequency at which the CPU operates is adjusted to the nominal clockfrequency in step 380 if the temperature is not below the temperaturethreshold.

However in some embodiments, an increase of the operating frequencyabove nominal operating frequency might momentarily be justifiable evenif the CPU temperature surpasses the threshold temperature. For example,it might be justifiable for a predetermined number of consecutivepositive polls. The increase of operating frequency may for examplealso, be justifiable for a predefined number of clock cycles or for theprocessing of a predefined number of instructions in the CPU.

While FIG. 3 illustrates the step 100, where an explicit pollinstruction is received, it should be understood that steps 370-390,could be combined with the implicit method of detecting polling and thealternative way of detecting positive and negative polls disclosed abovein regards to FIG. 2.

It should also be understood that a system configured to perform morethan one of the above example embodiments may be created.

FIG. 4 illustrates an example embodiment of a computer server 400comprising a CPU 410 and a control circuitry 420. In FIG. 4 only theelements necessary for the invention are disclosed. It should, however,be understood that the computer server 400 of FIG. 4 may comprisefurther elements and the disclosed elements may be part of, or comprise,further elements. For example, the computer server typically comprisesome persistent storage like an hard disk drive and a data bus forinterconnecting some of the elements with each other (neither explicitlydisclosed in the figure). The computer server 400 also comprises amemory unit 450, or storage medium, comprising an application 440; andan Input/output (I/O) range 430 associated with at least one I/O device(the device not explicitly shown in FIG. 4) for receiving input.

The application 440 is a set of computer readable instructions to beexecuted in the CPU 410.

The memory 450, while illustrated and referenced below as one memory,can comprise a set of memories. The memory 450 typically stores computerinstructions which are to be executed. The memory unit 450 is typicallya Random Access Memory (RAM), a Read Only Memory (ROM) or a non-volatilememory unit. In some embodiments of the present invention the storagemedium is a CD-rom disk, a blue-ray disk, a HDD (hard disc drive), a USB(Universal Serial Bus) unit connected to the computer server 400 or oneof the many other means suitable for storing computer readableinstructions.

Typically each I/O device comprises a range of I/O ports of which atleast one is addressed for each I/O operation directed at the device. Ingeneral, each of the I/O ports of the I/O devices within the computerserver is “numbered” to distinguish each I/O port from every other I/Oport. The number which identifies a particular I/O port is often calledits address. The computer server 400 may support Direct Memory Access(DMA) technique. The DMA technique allows for I/O devices to write andread data directly to and from the memory 450, via the data bus,surpassing the CPU 410. Typically, in order to support DMA the I/Odevice(s) and corresponding I/O ports(s) are mapped to a particularsection of the memory. The CPU 410 when instructed to read (or write to)the I/O device in such an instance typically reads (or writes to) theparts of the memory that the I/O port(s) on the I/O device are mappedonto.

The CPU 410, when executing an I/O read (or write) operation, typicallyaddresses one or more I/O port(s) of the I/O device but may for I/Ooperations also, as described above, address a section of the memory,when I/O ports are mapped to the memory 450. The term I/O range isherein used to interchangeably refer to: a single I/O port, multiple I/Oports or a set of memory address wherein each address corresponding to asection of the memory when I/O devices are mapped the memory; for whichinput can be expected to be received or found (when mapped).

In the example embodiment illustrated in FIG. 4, the CPU 410, in orderto perform a particular I/O operation, thus locates and addresses theI/O range 430 corresponding to the intended I/O ports of the I/O deviceto be affected by the particular operation.

In the example embodiment of FIG. 4 the CPU comprises the controlcircuitry 420. In some alternative embodiments the control circuitry 420is not part of the CPU 410 but is instead comprised in the computerserver 400 and coupled to the CPU 410 as indicated by an alternativedashed control circuitry.

The CPU 410 is associated with a nominal clock frequency and the controlcircuitry 420 is arranged to control the CPU 410. The CPU 410 is furthercoupled to an I/O range 430 and configured to deliver input received atthe I/O range 430 to an application 440. The control circuitry 420 isarranged to instruct the CPU 410 to poll the I/O range 430 for input tothe application.

The control circuitry 420 is also arranged to monitor whether or not apoll results in input to the application 440. The control circuitry 420is further arranged to adjust the clock frequency at which the CPU 410operates based on the result of the polling operation in accordance withone or several of the method steps 140, 180, 220, 240, 380 describedabove and illustrated in FIGS. 1, 2 and 3 respectively.

By monitoring whether or not each poll results in input, a number ofconsecutive polls rendering the same result can be detected. For examplea predefined number of consecutive polls rendering no input, negativepolls, may be detected. When detecting that a predefined number ofconsecutive negative polls have come to pass, the clock frequency fed tothe CPU is adjusted down to a predetermined first clock frequency lowerthan the nominal clock frequency. The continued polling for input willthen be performed at a frequency below the nominal frequency. As aresult fewer negative polls will be detected for each period of time.

The pre-defined number of polls allowed before the clock frequency atwhich the CPU operates is adjusted down is preferably chosen inaccordance with the requirements of a particular implementation asdescribed above in relation to the methods illustrated in FIGS. 1-3.

In some embodiments, the CPU 410 is configured to receive, from theapplication 440 an instruction to poll the I/O range 430 until a pollresults in input to the application. The CPU 410 is further arranged topoll the I/O range 430 in response to reception of the instruction fromthe application 440.

In some embodiments the control circuitry 420 is configured to controlthe CPU 410 to poll the I/O range 430 in response to reception of aninstruction from the application 440 to poll the I/O range 430 for inputto the application until a poll results in input to the application.

In some embodiments, the control circuitry 420 is arranged to monitorwhether or not a poll results in input to the application by monitoringread operations on the I/O range 430.

In some embodiments, the control circuitry 420 is configured to detectpolling of the I/O range 430. The control circuitry is further arrangedto detect a poll resulting in no input by being arranged to detect,within a predetermined number of instructions following a performed readoperation on the I/O range 430, a return to the same instruction to readthe I/O range 430.

In some embodiments, the control circuitry 420 is further arranged toadjust the clock frequency at which the CPU 410 operates, in accordancewith one or several of the steps 180, 240 described above andillustrated in FIGS. 1 and 2, to a predetermined second clock frequency,when a poll results in input to the application 440.

In order to allow for low latency, when a poll actually results ininput, the clock frequency at which the CPU operates is in someembodiments increased to a predetermined second frequency. In someembodiments, the predetermined second clock frequency equals the nominalclock frequency.

In some embodiments the predetermined second clock frequency is higherthan the nominal clock frequency. Typically the polling at a frequencylower than the nominal clock frequency consumes less energy than pollingat the nominal frequency. Thus, in situations where a number ofconsecutive negative polls higher than the pre-defined number of pollshave been performed and the operating frequency is reduced, less heatwill have been induced in the CPU. The CPU can in such situations for ashort time be allowed to operate at a frequency higher than the nominalclock frequency. This provides for a more thermally efficient systemwhere energy and heat generation is focused on situations where there isinput to process.

In some embodiments the control circuitry 420 is also arranged toperform the steps 370-380 described above and illustrated in FIG. 3.Thus, for some embodiments, the control circuitry 420 is furtherarranged to determine, when a poll results in input, a temperature ofthe CPU 410; and to compare the temperature of the CPU against apredefined temperature threshold. The control circuitry 420 is furtherconfigured to adjust the clock frequency at which the CPU 410 operatesto a predetermined third clock frequency higher than the nominal clockfrequency, if the temperature of the CPU is below the temperaturethreshold.

In situations where the temperature of the CPU can be determined to beless than a pre-defined temperature threshold, the operating frequencyof the CPU can be increased to a predetermined third clock frequencyhigher than the nominal clock frequency in order to reduce latency whenprocessing a received input.

In situations where the temperature of the CPU is above or equal to thetemperature threshold, operation of the CPU at a frequency higher thanthe nominal clock frequency may lead to overheating. In someembodiments, the control circuitry 420 is arranged to adjust the clockfrequency at which the CPU 410 operates to the nominal clock frequencyif the temperature is not below the temperature threshold.

In some embodiments, which are further elaborated on below in regards toFIG. 6, the CPU is arranged to poll the I/O range 430 by bypassing anoperating system kernel of the CPU 410. By letting the application,through the use of a hardware instruction library, poll the I/O rangedirectly the latency can be further reduced.

FIG. 6 illustrates a layered topology of data processing in accordancewith some embodiments. FIG. 6 is to some extent an alternative orcomplementary illustration of the computer server 400 illustrated inFIG. 4. Both the application layer and the kernel layer in FIG. 6relates to processing done in a CPU 410 of a computer server. Typicallyan application 640 when executed in the CPU 410 interacts with anoperating system, (OS) being executed in the CPU 410. The processing inthe CPU 410 prompted by the application is in FIG. 6 represented by theapplication layer. The application 640 corresponds to application 440 inFIG. 4. The OS is not explicitly disclosed in FIG. 6; however, theprocessing prompted by the OS is in FIG. 6 represented by the kernellayer. The main component of the operating system is typically referredto as an OS kernel. The OS kernel provides a bridge between theapplication 640 and the actual data processing in peripheral hardwaredevices 644 of the computer. Examples of such peripheral hardwaredevices 644 are an InfiniBand (IB) I/O controller card and a gigabitEthernet I/O controller card, but could be any type of network adapteror network interface card. Peripheral hardware devices 644 used forinput and output are below referenced as peripheral I/O devices. Eachperipheral I/O device is associated with at least one I/O port, and anysubset of all the I/O ports of all the peripheral I/O devices, couldconstitute an I/O range similar to the I/O range 430 previouslydisclosed in FIG. 4.

In the following OS and OS kernel is interchangeably used when referringto the operating system (while the OS not explicitly disclosed in FIG.6, the processing by the OS is in FIG. 6 represented by the kernellayer). The application 640 requesting resources or communicating with aperipheral device 644 (in hardware layer) is not required to haveexplicit knowledge of the peripheral device's 644 characteristics. TheOS kernel typically has a device driver installed for all connectedperipheral hardware devices 644. When the OS kernel receivesinstructions from the application 640, the OS kernel translates theinstructions into instructions comprehendible by the peripheral device644. Vice versa the OS can translate instructions/data from theperipheral hardware device 644 into a format comprehendible by theapplication 640. Double arrows 643 schematically illustrate a paththrough which the application 640 normally interacts with peripheralhardware devices 644. In order for the CPU 410 to switch betweenprocessing in application layer and processing in kernel layer a contextswitch is required.

While accessing system I/O resources typically is done through callsfrom the application 640 to the operating system kernel and induces atleast one context switch, it is possible for the application 640 tocomprise hardware instructions that are acceptable to peripheral I/Odevices 644. The application 640 in application layer can, by comprisinga hardware instruction library 641 with instructions suitable for aparticular peripheral I/O device 644 in hardware layer, interact withthe particular peripheral I/O device 644 directly as schematicallyillustrated by a double arrow 642 in FIG. 6, i.e. surpassing the kernellayer.

Sometimes it is advantageous to bypass an operating system whenperforming certain I/O tasks in order to further reduce the latency andincrease the throughput of a computer system. By bypassing the operatingsystem kernel, the application 640 with the use of the hardwareinstruction library 641 can control the CPU 410 to poll an I/O range430. By configuring the application through the use of a hardwareinstruction library to poll the I/O range directly, no context switchbetween the application and the OS kernel in the CPU 410 is necessaryfor the polling and the latency can be further reduced. Thus, in someembodiments, the CPU 410 is arranged to poll the I/O range 430 bybypassing an operating system kernel of the CPU 410.

An additional advantage of the disclosed method and the controlcircuitry is the ability to detect polling and detect a predeterminednumber of negative polls which allows the control circuitry to controlthe operations of the CPU regardless if the computer architecture allowsan application to bypass an operating system.

FIG. 5 illustrates an example embodiment of an automated exchange system500 comprising trader terminals 560 that are used for issuing order datamessages, i.e. input data, from clients to a central computer server,i.e. an automated exchange, 400 operating in accordance with one of theabove disclosed methods. The automated exchange 400 may e.g. be embodiedin accordance with the example computer server 400 illustrated in FIG.4. The trader terminals 560 are connectable, for example over theInternet 580, or over some other connection means like a dedicated fiber580B, to the automated exchange 400. The automated exchange 400 of FIG.5 may in some embodiments be embodied as a cluster of automatedexchanges. Sometimes the trader terminals 560 are connected to theautomated exchange 400 through an entry gateway 570. The entry gateway570 is connected to the central computer server hosting the automatedexchange 400, and is configured to receive market actions, i.e. ordersand/or quotes from the trader terminals 560. An entry gateway 570 isusually in connection with the automated exchange 400 on a dedicatednetwork and forwards the market actions to the automated exchange 400and further usually broadcast updates back to the trader terminals 560.It should however be understood that information being communicated toand from the automated exchange 400 and the trader terminals 560 couldbe communicated via a single communication path. Typically, theautomated exchange 400 matches the orders received from the tradingterminals in a matching process. The matching process of the automatedexchange 400 is one typical implementation of the application 440 inFIG. 4.

As mentioned above, the automated exchange 400 may be embodied inaccordance with the example computer server illustrated in FIG. 4. Forthis particular embodiment the central computer server 400 of theautomated exchange system 500 in FIG. 5, expressed in terms of thefunctional units of FIG. 4, comprises an input/output, I/O, range 430for receiving orders from trader terminals 560. The central computerserver also includes a CPU 410, coupled to the I/O range 430, and acontrol circuitry 420. The CPU 410 of the central computer server isassociated with a matching process for matching received orders,corresponding to the application 440 of FIG. 4. The matching process 440is arranged to control the CPU 410 of the central computer server topoll said I/O range 430 for received orders for input to the matchingprocess 440.

The central computer server of an automated exchange system (i.e. theautomated exchange) comprising a control circuitry in accordance withembodiments described herein has the advantage that incoming input (i.e.orders) can be detected and processed at an earlier stage than with aninterrupt driven process. The central computer server also has theadvantage that during troughs in load the automated exchange wastes lessclock cycles on negative polls. The reduced number of negative pollsleads to a more energy efficient server. Some embodiments of thecomputer server also have the advantage that as soon as an order isreceived and detected, the central computer server is ready to processthe order at nominal clock frequency, thus allowing for a highthroughput and a low latency. A central computer server of the presentinvention may thus allow for a low latency and energy efficientautomated exchange suitable for high throughput.

An advantage of certain embodiments described above is that incominginput, such as orders to an automated exchange, can be detected andprocessed at an earlier stage than with an interrupt driven process.Another advantage of some of the embodiments is that that during troughsin load less clock cycles are wasted. Hence by reducing the number ofnegative polls the system becomes more energy efficient. A furtheradvantage of some of the embodiments is that as soon as an order isreceived and detected the central computer server is ready to processthe order at nominal clock frequency, thus allowing for a highthroughput and a low latency. An additional advantage of some of theembodiments is that the energy consumption is reduced by polling at areduced frequency. By operating the CPU at a reduced frequency lesselectrical energy is also converted in thermal energy, allowing for theoperating frequency of the CPU to be increased above the nominaloperating frequency when processing a received input. This may in turnallow for latency to be reduced considerably and throughput to beincreased while maintaining a stable system.

The present invention is not limited to the above-described preferredembodiments. Various alternatives, modifications and equivalents may beused. Therefore, the above embodiments should not be taken as limitingthe scope of the invention, which is defined by the appended claims.

1. A method for controlling operations of a Central Processing Unit,CPU, associated with a nominal clock frequency, the CPU being coupled toan input/output, I/O, range and configured to deliver input to anapplication, the method comprising controlling the CPU to poll the I/Orange for input to the application, wherein the polling is repeateduntil a poll results in input to the application, the methodcharacterized by: monitoring whether or not each poll results in inputto the application; and adjusting a clock frequency at which the CPUoperates, to a predetermined first clock frequency lower than thenominal clock frequency, if a pre-defined number of polls resulting inno input is detected.
 2. The method according to claim 1, wherein theCPU is controlled to poll the I/O range in response to reception of aninstruction, from the application, to poll the I/O range for input tothe application until a poll results in input to the application.
 3. Themethod according to claim 1, wherein the monitoring involves monitoringread operations on the I/O range, and a poll resulting in no input isdetected by detecting, within a predetermined number of instructionsfollowing a performed read operation on the I/O range, a return to thesame instruction to read the I/O range.
 4. The method of claim 1,wherein the pre-defined number of polls equals one.
 5. The method ofclaim 1, wherein the method further comprises: adjusting the clockfrequency at which the CPU operates, to a predetermined second clockfrequency higher than the predetermined first clock frequency, if a pollresults in input to the application.
 6. The method of claim 5, whereinthe predetermined second clock frequency equals the nominal clockfrequency.
 7. The method of claim 5, wherein the predetermined secondclock frequency is higher than the nominal clock frequency.
 8. Themethod of claim 1, wherein the method further comprises: determining,when a poll results in input, a temperature of the CPU; comparing thetemperature of the CPU against a predefined temperature threshold; andadjusting the clock frequency at which the CPU operates to apredetermined third clock frequency higher than the nominal frequency,if the temperature of the CPU is below the temperature threshold.
 9. Themethod of claim 8, wherein the clock frequency at which the CPU operatesis adjusted to the nominal clock frequency if the temperature is notbelow the temperature threshold.
 10. The method of claim 1, wherein thepolling is performed by bypassing an operating system kernel of the CPU.11. A control circuitry for controlling a Central Processing Unit, CPU,associated with a nominal clock frequency, the CPU being coupled to anI/O range and configured to deliver input received at the I/O range toan application, characterized in that the control circuitry is arrangedto: instruct the CPU to poll the I/O range for input to the application;monitor whether or not a poll results in input to the application; andadjust a clock frequency at which the CPU operates, to a predeterminedfirst clock frequency lower than the nominal clock frequency, if apre-defined number of polls of the I/O range resulting in no input isdetected.
 12. The control circuitry of claim 11, wherein the controlcircuitry is configured to control the CPU to poll the I/O range inresponse to reception of an instruction, from the application to pollthe I/O range for input to the application until a poll results in inputto the application.
 13. The control circuitry of claim 11, wherein thecontrol circuitry is arranged to monitor whether or not a poll resultsin input to the application by monitoring read operations on the I/Orange, and the control circuitry is arranged to detect a poll resultingin no input by being arranged to detect, within a predetermined numberof instructions following a performed read operation on the I/O range, areturn to the same instruction to read the I/O range.
 14. The controlcircuitry of claim 11, wherein the pre-defined number of polls equalsone.
 15. The control circuitry of claim 11, wherein the controlcircuitry is further arranged to adjust the clock frequency at which theCPU operates, to a predetermined second clock frequency higher than thepredetermined first clock frequency, if a poll results in input to theapplication.
 16. The control circuitry of claim 15, wherein thepredetermined second clock frequency equals the nominal clock frequency.17. The control circuitry of claim 15, wherein the predetermined secondclock frequency is higher than the nominal clock frequency.
 18. Thecontrol circuitry of claim 11, wherein the control circuitry is furtherarranged to: determine, when a poll results in input, a temperature ofthe CPU; compare the temperature of the CPU against a predefinedtemperature threshold; and adjust the clock frequency at which the CPUoperates to a predetermined third clock frequency higher than thenominal clock frequency, if the temperature of the CPU is below thetemperature threshold.
 19. The control circuitry of claim 18, whereinthe control circuitry is arranged to adjust the clock frequency at whichthe CPU operates to the nominal clock frequency if the temperature isnot below the temperature threshold.
 20. The control circuitry of claim11, wherein the CPU is arranged to poll the I/O range by bypassing anoperating system kernel of the CPU.
 21. A central computer server of anautomated exchange system for matching orders received from clientscomprising an input/output, I/O, range for receiving orders from clientsof the automated exchange system; a Central Processing Unit, CPU,associated with a matching process for matching received orders, the CPUbeing coupled to the I/O range, the central computer servercharacterized by: further comprising a control circuitry according toclaim 11 for controlling the CPU to poll said I/O range for receivedorders for input to the matching process.